RE: Object instantiation in C#

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> - If I declare a property as a user-defined object (ie as a reference) how
> can I test to see if it has been instantiated (assigned) or not?

Check if it is null. All objects in C# default to their default values if
you don't explicitly instantiate/initialize them. The default value for
reference types is null.

e.g.

MyObject obj;

if(obj == null)
{
obj = new MyObject();
}

> - If I use 'new' to instantiate an object, but the reference variable I use
> already refers to an instantiation of the class, is the reference variable
> reassigned, and if so what happens to the object it previously referenced
> (which is now presumably completely inaccessible)?

I assume you mean something like this:

MyObject object1 = new MyObject();

object1 = new MyObject(); // Reassigning it.

Basically object1 now points to a new object. The old object will be garbage
collected.

Hope this helps.

Ah, you might find this C# for C++ programmers FAQ useful:
http://www.andymcm.com/csharpfaq.htm

--
Brian Delahunty
Ireland

http://briandela.com/blog

INDA SouthEast - http://southeast.developers.ie/ - The .NET usergroup I
started in the southeast of Ireland.


"Dave" wrote:

> I come form a C++ background and am new to C#. I am puzzled by the object
> instantiation mechanism, and would be grateful if someone could clarify the
> following related questions:
> - If I declare a property as a user-defined object (ie as a reference) how
> can I test to see if it has been instantiated (assigned) or not?
> - If I use 'new' to instantiate an object, but the reference variable I use
> already refers to an instantiation of the class, is the reference variable
> reassigned, and if so what happens to the object it previously referenced
> (which is now presumably completely inaccessible)?
> --
> Dave
.

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